The commercially important dimethyl adipate, a compound of the general formula I, may be prepared, as described in U.S. Pat. No. 4,256,909, by the following steps: reacting 1,3-butadiene with carbon monoxide and methanol with formation of methyl pentenoate in the presence of a tertiary nitrogen base and a cobalt carbonyl catalyst; removing the greater part of the tertiary nitrogen base and excess hydrocarbons, and reacting the methyl pentenoate thus obtained with carbon monoxide and methanol in the presence of a cobalt carbonyl catalyst and the residual amount of tertiary nitrogen base to give dimethyl adipate.
A disadvantage of this known process is that step (a) requires the use of extremely high pressures, such as from 600 to 1200 bar.
It is an object of the present invention to avoid the use of extremely high pressures.